Recently, with the growth of urban and industrial areas, and the shortage of land and high-quality materials, demand for use of marginal lands is increasing. Additionally, techniques and equipment for improvement of loose and soft soil have been proposed. Generally, soft cohesive soils have two main characteristics, the first one is the low shear strength, and the second one is large settlement. Furthermore, loose granular soils have the great potential of liquefaction.
In the last few decades, compaction using sandy or gravelly columns, pile, piers, etc., has been conducted all over the world as a technical and an economical method. In practice, various methods of compacting gravelly piers were founded on one of the construction replacements, construction displacement, or combination methods. However, the final products, construction process, the configuration, and the effect on the relative density of gravel and matrix soil, which were constructed by each of the aforementioned methods, are very different. Generally, the gravel piers constructed by construction methods which are based on the type of loading, mechanical and physical characteristics of soil layers, and environmental conditions, are divided into multiple categories, for example, stone columns, compaction piles, rammed aggregate piers, etc.
Typically, stone columns are constructed by replacement of loose material with gravelly material by two methods of vibrating replacement and vibrating compaction. Compaction piles are constructed based on displacement mechanism by means of excavating a hole in the ground and making a radial compaction for the surrounding soil and filling it by sandy or gravelly material by two methods of sand compaction piles and gravel compaction piles. Rammed aggregate piers are made of methods based on the combination of replacement and displacement, and by means of excavating a hole by mechanical auger, filling it by gravelly material and making a radial compaction in the layers.
The present disclosure relates to an excavation process, and more particularly relates to a system and method for forming a compacted aggregate pier at a target location. The technologies and processes offered in the prior art perform in loose and coastal submerged soils. However, the mandrel accidently collides in its path with a very dense sandy intermediate layer which will result in the creation of tolerance beyond the main objectives of this method. On the other hand, the cost and the implementation time would increase. Moreover, assuming cross through the intermediate layer by the primary hole, the operation of gravel compaction into the well by the long penetrating tamper will be challenged especially in the lower half of pier due to the difficulty in pulling up the mandrel.
Therefore, there is need for an improved system and method for making gravel impact compaction piers, which increase the density of loose soils or soils with dense sandy intermediate layers especially in shores and rivers, in submerged conditions, and increase the bearing capacity and the subgrade reaction modulus and decrease the soil settlement.